Electrical4U What is a Shunt Resistor? A current-sense shunt is a precisely known, low-value resistor placed in series with an electric current path. Current creates a small voltage drop across it, allowing a meter or control circuit to calculate current. Precision shunts often use a low-temperature-coefficient alloy so their resistance changes little with temperature. In a … Read more
What is a Berry Type Transformer? A berry type transformer has a laminated core that radiates from the centre like the spokes of a wheel. Texts also call it a berry transformer. On core layout, machines of this kind are grouped as: A berry type transformer is a shell-type construction. The radial core is why … Read more
What is Ohm’s Law? Ohm’s law states that the current through an ohmic conductor is proportional to the voltage between its ends, if temperature and other physical conditions stay fixed. That ratio V/I is the resistance R of the sample under those conditions. In symbols Ohm’s law is Write the constant of proportionality as resistance … Read more
What is a Transformer Connection? A three-phase transformer connects each three-phase winding in star (Y) or delta (Δ). The primary and secondary choices together set the voltage ratio, the phase shift and whether a neutral is available. The bank can be three single-phase units or one three-limb (or five-limb) core. One three-phase core uses less … Read more
What is Stroboscopic Motion? Stroboscopic motion (also called the stroboscopic effect) is the aliasing of a repeating movement when you see it in short samples instead of a steady view. It shows up when the sampling rate, such as a film frame rate or a flash rate, is close to the rotation frequency or a … Read more
What is Electrical Resistance? Electrical resistance is the opposition to current in a circuit. For an ohmic conductor it equals voltage divided by current. The SI unit is the ohm (Ω), written with the Greek letter omega. A larger resistance lets less current through for the same voltage. When a potential difference is applied across … Read more
What is Clamping Voltage? Clamping voltage is the residual voltage an SPD lets through while conducting a surge. An electrical circuit breaker interrupts current. A surge protector uses that clamp level so downstream equipment sees a limited surge voltage. On a datasheet the clamp figure (UL 1449 voltage protection rating, VPR) is the voltage measured … Read more
What is a Dead Short? A dead short is an unintended path that lets current bypass the load with (ideally) no resistance or impedance. The resulting current is limited only by the source and the shorting conductor, so it can destroy equipment and shock anyone nearby. Finding a dead short is hard because the current … Read more
What is a Latching Relay? A latching relay is a two-position electromechanical switch. A magnetic or mechanical latching type holds its contacts after a short coil pulse, so the coil does not need power to stay in that state. A standard relay wired with a holding contact is also called a latching circuit, even though … Read more
What is Rise Time? Rise time is the time a waveform takes to go from a stated low level to a stated high level. In analog and digital work those levels are usually 10% and 90% of the final (steady) value. Some logic families quote 20% to 80% instead. In analog circuits it is the … Read more